cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
arefrateb
Observer
Observer
1,621 Views
Registered: ‎03-24-2018

why high impedance consume more power?

i'm trying to reduce power consumption in my algorithm so i decided to make data_substituted and data_permuted equal to high impedance (Z) when the round

is even as this figure shows 

modsim.PNG

instead of this orgsim.PNG

 

in order to reduce the power, but the power increased in first pict instead of decreased  which is illogical

this pic shows the power consumption in first scenario

pw2.PNG

tim2.PNG

and this pic shows the power consumption in Second scenario

power 1.PNG

 

ti1.PNG

these results done under the same constrains: create_clock -period 3.200 -name ACLK -waveform {0.000 1.600} [get_ports ACLK]

*when run implementation  for the first scenario (first pic), i have tow critical warning that i don't understand them and i don't know if the critical warning caused this illogical result.

pic1.PNG

 

 

 pic2.PNG

 

****************************************************

other critical warning for both scenarios. 

vi.PNG

what should  i do and how to make the power for the first Pict (first scenario) less than the second one ?

**modified code and original one in the attachments.

0 Kudos
Reply
6 Replies
drjohnsmith
Teacher
Teacher
1,596 Views
Registered: ‎07-09-2009

which chip do you have with internal tri states ?

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
0 Kudos
Reply
arefrateb
Observer
Observer
1,590 Views
Registered: ‎03-24-2018

ch.PNG

0 Kudos
Reply
arefrateb
Observer
Observer
1,554 Views
Registered: ‎03-24-2018

i also tried virtex 7 and unfortunately the same result obtained 

0 Kudos
Reply
drjohnsmith
Teacher
Teacher
1,537 Views
Registered: ‎07-09-2009

The seven series does not have internal tri state

 

If you code tri state, 

    the tools convert that to an internal MUX, 

 

which if it meets timing , will not be optimised away,

 

 

I thin some of the old Spartan were the last chips that declared real internal tri states.

 

tri states are only for external signals, 

    and the IO drivers do support tri state.

 

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
0 Kudos
Reply
arefrateb
Observer
Observer
1,533 Views
Registered: ‎03-24-2018

so what should i do to turn the data substituted and permuted off , or turn the clock off somehow in even rounds as the first figure in order to reduce the power?

0 Kudos
Reply
drjohnsmith
Teacher
Teacher
1,508 Views
Registered: ‎07-09-2009

How to save power , now thats a new question,

 

suggest you start a new thread,

 

in the mean time, 

 

https://www.xilinx.com/support/documentation/sw_manuals/xilinx2014_1/ug907-vivado-power-analysis-optimization.pdf

 

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
0 Kudos
Reply